1974 135 hp performance

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N Wolf

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I recently blew up the second 1991 90 hp force on my 17ft astro bass boat.
I needed a motor to finish out the season and found a 74 135 evenrude for a steal. My question is what kind of performance can I expect from this old motor. I have 130lbs on all cylinders and it starts and runs perfectly. however it doesnt have tilt and trim. With the motor set all the way down it didnt want to get on plane and only gave me a top speed of 37 mph at 5000rpm. The prop was a little damaged when I started. I have a new one on it now and havent run it yet. They are both 13x19s. I dont know what kind of rpm or speed I should be getting out of this motor but two weeks ago I was on a boat just like mine with a 115 merc that did 51 on the gps.
 
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ezeke

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Re: 1974 135 hp performance

The 1974 135HP engine is the equivalent of a 115HP in the current horsepower rating system.

The gear ratio of the motor was 1.923077. (13:25): http://go-fast.com/Prop_Slip_Calculator.htm

The maximum theoretical speed with zero slip and a 19 pitch propeller at 5000 RPM is 47 MPH.

5000 RPM max at WOT is too low; you need to be able to reach 5800 with your average load to prevent lugging the engine and drastically shortening its useful life. 15 pitch is indicated and no more than 17.

You may be able to achieve 5800 RPM by changing the setup.
 
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N Wolf

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Re: 1974 135 hp performance

The prop was pretty banged up. How much efect could that have on my max RPM? I have never had an alum prop before so I have no idea what one that bad could do. By the way the last motor that was on it was a 1990 force 90 with one dead cylinder and it would push the boat to 33mph GPS at 5200 rpm so I highly doubt that even at a true 115 hp the evinrude couldnt spin the same prop for beter speed. The hull is still made by procraft and can carry 32 mph with a 50hp witch is the smallest offered, a 90 = 45 mph and a 115 = 47. These are verified numbers with my hull. Like I said I only get 37. So my real question is would a banged up prop cause this much of a power loss or is there some other problem that would cause low power like that while still purring along? I will check everything again with the new prop and see what the difference is.
 
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N Wolf

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Re: 1974 135 hp performance

That may have sounded bad, sorry bout that. Its not realy fair of me to ask advice without giving you all the info. First I will post some pics of the prop so that you know what "banged up" means. Here are the rest of the facts. The motor came off of a 1973 rincon 18ft runabout. Its a big dang boat. It is now on a 1993 astro 17xs bass boat. It is on a 6" set back jack plate set as high as I feel comfortable with becouse of the high water pickup on this motor. I wired it up to my tach without making any changes. The motor does not have tilt and trim so I have it set at the second spot up. I ran it once at the third hole but had to put my girlfreind on the deck to bring it on to plane.
No diference in speed. The prop got messed up by me. More on this later today when I send the pics.
 
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ezeke

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Re: 1974 135 hp performance

The pitch of the propeller determines the theoretical maximum speed. a 19 pitch propeller can move 19 inches for each revolution of the propeller under conditions where there is absolutely no resistance.

You cannot compare motors by RPM without knowing the gear ratios.

There is virtually no power difference between a modern 90HP crossflow Evinrude and a 1974 135 until you reach above 5000 RPM, just as there was little difference between the 115 and the 135 in 1974 until you hit the high RPM.
 
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R.Johnson

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Re: 1974 135 hp performance

Did you check compression, or fuel flow on this engine you got for a steal. Unless you have a very heavy, large boat, nobody should have to get out of their seat, and move forward to make it plane. That old 135 should be more than a match for a 90 HP Force.
 
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N Wolf

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Re: 1974 135 hp performance

I know what pitch is. You may not mean to say this but what you are saying is that a 1974 evinrude 135 puts out about the same power as a 1991 force 90hp with one blown cylinder. The blown up force could still spin up to 5200 with the same prop. I know they dont have the same gearing but the 135 should be able to compete with a good 115, that is what you said. Proping down is not the answer to a weak motor. A good 115 can spin a prop that can push my boat to 47 mph. The 19 pitch should get close, a 15 wont.
 
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ezeke

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Re: 1974 135 hp performance

You started this discussion by saying you could only reach 5000 RPM at WOT. No matter what the reason, that is inadequate for the best performance of the motor and to sustain the life of the engine.
 
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N Wolf

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Re: 1974 135 hp performance

Yep, I have checked compresion. 130 on all 4, could be 131 or 2 but my gauge only has 5lb increments. fuel is good at low speeds but I dont know how to check that at speed. I also have good spark at idle on all 4. Static timing is aboat 18 degrees. I havnt checked it running, kind of a hard thing to do by yourself. As I said before about the prop I tore it up on the first run. I took off in an ox bow that is a constant 4 feet deep. When it stood up it didnt want to come over the top and then hit botom and cavitated. No big deal on mud with an ss prop but I guess an aluminum one doesnt like that much.
I have heard of a way to check the fuel at high speeds but I dont remember it. I think it goes something like this. Install new plugs, get up to speed, run it for a bit then kill it at full throtlle so that you can read the plugs. If you throtle down then kill it the last mixture to hit the plugs would be the low speed mix. Sound right? Sounds like a good way to swamp to me but then, I've never tried it.
Oh, one more thing I may not have mentioned. I had to put a fin on it. Ok, two things. It hesitates going from a fast idle to full trottle. Actually it died twice and it was plenty warm when it happened.
 
ondarvr

ondarvr

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Re: 1974 135 hp performance

Lots of stuff going on here, with bits and pieces of new information slipping in periodically.

How do you know the tach will work correctly with this motor? you will most likely need to change the settings on it.

If the motor died twice, there is something wrong, probably fuel related, clean the carbs and check for leaks.

Don't bother trying to set it up with a damaged prop. (if its more than a slight ding)

"I had to put a fin on it" Why?
 
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N Wolf

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Re: 1974 135 hp performance

"I had to put a fin on it" means it wont get on plane without it.
 
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N Wolf

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Re: 1974 135 hp performance

The motor sat for two years before I got it. I have done every thing to it that I know to do to bring it back to life. I have to admmit though that I know nothing about carberators. What would cause it to stall like that? The fuel system leading to the motor is all new.
 

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N Wolf

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Re: 1974 135 hp performance

You sure? Cause Im a little nervouse about taking them apart. I'll do it if thats what it needs, but this isnt the same kind of risk as doing it on my lawn mower. I dont want to risk my tournament season either. By the way, is that prop as bad as I think it is?
 
cougar1985

cougar1985

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Re: 1974 135 hp performance

N Wolf said:
You sure? Cause Im a little nervouse about taking them apart. I'll do it if thats what it needs, but this isnt the same kind of risk as doing it on my lawn mower. I dont want to risk my tournament season either. By the way, is that prop as bad as I think it is?
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seen props worse than that.did you check to make sure that the prop doesnt have a spun hub?it could be slipping .scribe a mark on the hub rubber and one on the surrounding metal ,if after running they dont line up anymore you have a spun hub.all things being equal theres no way in hell that a 90 force could beat a 135 omc.
 
ondarvr

ondarvr

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Re: 1974 135 hp performance

Its not very difficult to clean a carb and it doesn't take very long either and Its most likely the only way to get it running correctly too. You'll surprise yourself with your new found skill, in fact it will probably lead to more mechanical projects being conquered.

That prop is in bad shape and should be fixed before you try get everything dialed in.
 
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N Wolf

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Re: 1974 135 hp performance

I wouldnt think so either. As for the spun hub, I just put a brand new prop on it and havent ran that one yet. As for the carb cleaning, these things dont look like any carbs I've ever seen. Little scared.
 
cougar1985

cougar1985

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Re: 1974 135 hp performance

N Wolf said:
I wouldnt think so either. As for the spun hub, I just put a brand new prop on it and havent ran that one yet. As for the carb cleaning, these things dont look like any carbs I've ever seen. Little scared.
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it takes longer to get the carbs off than to rebuild .get a manual if you can their invaluable.its not rocket science ,you will be asking your self what the heck was i scared for after you tackle them.remember on important thing ,most kits cover several models so you wil have parts left over ,dont panic!even the omc kits have extra parts in them that cover differnt years.
 
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N Wolf

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Re: 1974 135 hp performance

10-4, thanks guys I will try to get the parts in and see how it goes.
 
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emdsapmgr

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Re: 1974 135 hp performance

The timing on that engine may be low. That will affect it's overall performance. There should be a factory label on the airbox which will indicate the max degrees of timing at 5000 rpm. (It should probably be set around 28 degrees.) You should verify the timing when running it and set it according to the original factory service manual.
 
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